DS12887 DATASHEET PDF
DS, DS Datasheet, DS Real Time Clock, buy DS The DS, DS, and DS12C real-time clocks (RTCs) are Pin Configurations and Ordering Information appear at end of data sheet. WWW. Y. DESCRIPTION. The DS Real Time Clock plus RAM is designed to be a direct replacement for the DS The DS is identical in form, fit, and.
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Pin-compatible with the MCB and. Totally nonvolatile with over 10 years of. Self-contained subsystem includes lithium. Counts seconds, minutes, hours, days, day of.
Binary or BCD representation of time. Daylight Savings Time option. Selectable between Motorola and Intel bus. Multiplex bus for pin efficiency. Interfaced with software as RAM.
Programmable square-wave output signal. Bus-compatible interrupt signals IRQ. Three interrupts are separately software. Periodic rates from ms to ms. Underwriters Laboratory UL recognized. Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device. For information about device errata, click here: The DS is identical in form, fit, and function to the DS, and has an additional 64 bytes of. Access to this additional RAM space is determined by the logic level presented on.
DS12887 RTC INTERFACING
AD6 during the address portion of an access cycle. A lithium energy source, quartz crystal, and write. As such, the DS is a. The functions include a nonvolatile. The RTC is unique in that time-of-day and memory are maintained even in the. The block diagram in Figure 1 shows the pin connections with the major internal functions of the.
The following paragraphs describe the function of each pin. When V CC falls below 4. When the DS is in a write-protected state, all inputs are ignored and all.
When V CC falls below a level of approximately 3V, the external. V CC supply is switched off, and an internal lithium energy source supplies power to the RTC and the. DC power is provided to the device on these pins. When V CC is. However, the timekeeping function continues.
The timekeeping function maintains an accuracy of? C, regardless of the voltage daatsheet on the V CC pin. The MOT pin offers the flexibility to choose between two bus types.
When connected to GND or left disconnected, Intel. The pin has an internal pulldown resistance of approximately 20k W. The SQW pin can output a signal from one of 13 taps provided by ds112887.
The frequency of the SQW pin can be changed by programming. Register A, as shown in Table 1. Multiplexed buses save pins because.
The addresses are present. Addresses must be valid. Valid write data da12887 be present and held stable during the latter portion of the DS or WR pulses. Motorola timing or as RD transitions high in the case of Intel timing. AS Datasjeet Strobe Input? A daasheet address-strobe pulse serves to demultiplex the bus. The next rising edge that. DS is a positive pulse during the latter portion of the bus cycle and is called Data Strobe. In write cycles the trailing.
RD identifies the time period when. The RD signal is the same definition as the output-enable. OE signal on a typical memory. When the MOT pin is. A write cycle is indicated. The chip select signal must be asserted low for a bus cycle in the DS to. Bus cycles that take place without asserting CS latch addresses but no access.
When V CC is below 4. The IRQ output remains low as long as the status bit causing the. To clear the IRQ pin, the processor. When no interrupt conditions are present, the IRQ level is in the high-impedance state. The IRQ bus is an open drain output and requires an. RESET pin can be held low for a time to allow the power supply to stabilize. The amount of time that. RESET is held low is dependent on the application. Periodic Interrupt Flag PF bit is cleared to 0.
Alarm Interrupt Flag AF bit is cleared to 0. Dwtasheet pin is in the high impedance state. This connection allows the DS to go in. The address map of the DS is shown in Figure 2.
DS RTC INTERFACING
The address map datasbeet of bytes of user. All bytes can be directly written or read except for the following: The time and calendar information is obtained by reading the appropriate memory bytes. The contents of the In addition to writing the Register B must be set to the appropriate logic level. All 10 time, calendar, and alarm bytes must use the. The set bit in Register B should be cleared after the data mode bit has been written fatasheet. Once initialized, the RTC makes all updates in the.
The data mode cannot be changed without reinitializing the 10 data bytes.
When the hour format is selected, the high-order bit. The time, calendar, and alarm bytes are always. The 10 bytes are advanced once per second by 1 second and.
If a read of the time and calendar data occurs during an update, a problem. The probability of reading incorrect time. Several methods of avoiding any possible incorrect time and calendar reads are. The three alarm bytes can be used in two ways. First, when the alarm time is written in the appropriate. The second use condition is to insert a “don’t care” state in one or more of. The “don’t care” code is any hexadecimal value from C0 to FF.
An alarm is generated each. Similarly, an alarm is generated every minute. The “don’t care” codes in all three alarm. Day of the Week. Date of the Month. They can be used by the processor program as nonvolatile memory and are fully available during the. The update-ended interrupt can be used ds128877.
Each of these independent interrupt conditions is.